Conversion of oils



May 23,1944 vc. w. TYsoN ET AL CONVERSION OF OIL Filed June 12, 1940 Ngftu X NN www w Y Nw N .lvwhl Y l NN v MN bw Nm IIII' Mioqvxv w NM1..

Patented May 23, 1944 CONVERSION F OILS Charles W. Tyson, Summit, and Carli). Tongberg,

Westfield, N. J., assignors to Standard Oil Developnient Company, a corporation of Delaware 'Application June 12, 1940, serial No. 340,070

(ci. 19a-.52

4 Claims.

This invention relates to the conversion of hydrocarbon oils and pertains more particularly to the conversion of suchl oils in the presence of finely divided solid catalytic material which is subjected to frequent regenerations.

While the invention in some of its broader phases has a more general application such as in processes involving the reforming, dehydrogenation, polymerization, alkylation and isomerization of hydrocarbon oils and also in the purifying and refining of such oils, it finds particular application in the cracking of higher boiling hydrocarbons into lower boiling constituents suitable for motor fuel.

It has heretofore been proposed to crack hydrocarbon oils by suspending finely divided cracking i catalysts in a stream of oil to be cracked and then passing .theA resulting stream through a cracking zone maintained at the desired cracking temperature. When operating in this manner the cracked products containing the catalyst in suspension after passing through the cracking zone are first transferred through suitable separators for segregating the powdered catalytic material from the i cracked products. The cracked products are then fractionated to separate the motor fue] fraction from insufficiently cracked constituents and gases. The finely divided catalytic material after passing one or more times through the cracking zone is passed through a regeneratingy zone in which an oxidizing atmosphere is maintained to burn off carbonaceous and otherl combustible deposits which form during the' cracking process and which tendto reduce the activity ofthe catalyst. One 'method of regenerating such finely divided catalytic materialis to suspend the catalyst recovered from the separators in a stream of gas and pass the resulting stream through a regenerating zone in which an oxidizing atmosphere is maintained under conditions such as to burn the carbonaceous deposits from the catalyst. The stream of regenerating gas and catalyst after passing through the regenerating zone is then transferred to suitable separators of the same or different type than those employed in segregating the catalyst from the cracked products. The regenerated catalyst separated from the regenerated gas in the separators is then returned to the cracking process for reuse.

This method of regenerating combined with powdered catalyst cracking offers a number of advantages resulting in lower equipment and operating costs.

In order to obtainmaximum efficiency from a combination process above described it has heretofore been considered desirable to maintain a 55 It has been discovered as a result differential pressure between the cracking and regenerating portions of the equipment. For example experience has shown that., in most cases at least, the maintenance of a substantial superatmospheric pressure in the cracking zone results in excessive formation of coke on the catalyst and also changes the characteristics of the motor fuel produced. On the other hand the use of a substantial superatmospheric pressure in the regeneration portion of `theequipment permits better control of the regenerating temperature andreduces the size of the equipment.

Practical difficulties have been encountered however in devising operating equipment which will transfer the finely divided catalytic material from the zone of lower pressure such as that employed in the cracking circuit into a zone of higher pressure such as is employed in the regenerating circuit. By way of example, if a compression screw or other mechanical means is employed for imposing the desired pressure on the catalyst it has been found that the power requirement increases wi'th the difference of pressure across the compression screw. Furthermore a high pressure differential across the screw tends to increase wear and erosion on the screw and tends to increase maintenance costs. l

Also serious operating difficulties have been encountered in releasing the pressure on the cat-v alyst stream between the regenerating and cracking zone. Attempts made to release thegpressure by means of rotary star feeders, Venturi tubes, release valves and other similar mechanical means .have not proven wholly successful. In case of the star-feeders, for example, diiliculty has been encountered fln regulating the flow catalyst throughl the feeder. Due to the finely divided nature of the catalyst, a considerable portion passed through the clearances in the feeder and around the empty return pockets in the feeder. In the case of restricted openings', such as Venturi tubes, the catalyst tends to bridge across the restricted openings and plug the lines. Release valves are subject to the same objection as the Venturi tubes and further introduces erosi'on problems.

Among the objects of the present invention is to provide a method of overcoming the difliculties above-mentioned and to provide a process wherein the cracking and regenerating portions of the equipment may be operated under substantially the same pressure without the inherent objections previously attending such operations.

Other objects and advantages of the invention will be apparent from the more detailed descrip- 4 tion hereinafter.

o'f extensive amount of coke formed when cracking under super-atmospheric pressure as when cracking at atmospheric pressure providing the partial pressure ofthe oil vapors is the same in both cases.

The total pressure in the cracking circuit may be increased without increasing the partial pressure of the oil vapors by introducing a diluent or inert gas. Such 'gas may for example be steam or it may be a gas capable of undergoing reactions other than cracking'such as capable of undergoing polymerization,` alkylation, isomerization, etc. While steam, due to its availability and cost is preferred, other gases such as those formed during the cracking operation maybe employed.

Having set forth the general nature and objects, the invention will be better understood by referring to the accompanying drawing which is partly diagrammatic and partly schematic of an apparatus capable of carrying the invention into eect. I

Referring to the drawing, a numeral id 'designates a charge line through which the oil to be cracked is introduced into the system. Such oil may comprise a clean condensate stock such as a gas oil or it may be a residual stock such as a topped or reduced crude. The oil introduced through the line I0 is forced 'by pump il through a heating coil i2 located in furnace i3 wherein it is heated to a temperature sumcient to vaporize at least a substantial portion of the oil. The temperature and time of contact of the oil within the heating coil i2 is preferably controlled to obtain the desired degreeof vaporization without any substantial amount of thermal cracking.

Ii' desired steam or other diluent gas may be introduced into the-oil passing' to the vaporizing v coil through line i4.

The oil after passing through the vaporizing coil i2 .is conveyed through transfer line i5 to a separator i6 wherein vapors separate from the unvaporized residue. Steam or other diluent gas may be introduced into the bottom of the separator i6 through line i'i. Unvaporized residue separated in the separator it may be withdrawn from the bottom thereof through line i8. Vapors liberated in the separator it pass overhead I through line i9 to an injectorv 26 in which nnely divided catalytic materialis introduced into 4the stream. y Y t In cases where a vclean condensate stock is emi ployed for crackingl the separator .I6 may he -omitted or the products from the vaporizing coil i2 may be passed around the separator through lin 2i. l

A catalyst introduced into the oil vapors in the injector may be'any suitable catalyst capable of accelerating vor bringing about desired cracking operation. Such catalysts maycomprise for example the naturally active or activated clays i or nal cyclone separator 2l for further puri-- orv synthetic adsorptive materials of the same or diierent chemical composition.'

The relative amount of, catalyst introduced into the oil vapors is dependent upon the activity idof the catalyst, the nature of the oil to be cracked, the temperature of the cracking operation, the degree of conversion desired and other factors. In general the relative amount of catalyst to oil vapors may range between .5 up to 20 or more parts of catalyst per part of oil.

The suspension of oil vapors, inert gas, and finely divided catalyst formed in the injector -20 passes'through line 22 to a cracking reactor 23. The reactor 23 may be of any suitable design capable of maintaining the catalyst in suspension Within the gas stream and for giving the required time for obtaining the conversion. illustrated, the reactor 23 is shown in the form of a vertical tower which is preferably insulated to avoid radiation losses. It will he understood however that any other type of apparatus such as fired or unred coils, baille towers or the like may be substituted in its stead.

The suspension after passing through the reactor 23 in which the cracking operation is accomplished is transferred through line 24 to suitable equipment for separation of the catalyst 'from the cracked products. Such equipment may for example comprise a plurality of cyclone separators 25, 26 and 2li connected in series through lines 28 and 29. Catalyst separated in the initial cyclone separator 25 is removed from the bottom thereof through conduit 3i and passed to a catalyst hopper 32. If desired steam or other stripping gas may ble introduced into the stream of catalyst passing through the catalyst hopper 32 through line 33 for removing volatile hydrocarbon constituents remaining in the catalyst.

The cracked products, after having the bulk of the catalytic material removed therefrom in the vinitial cyclone separator 25, pass through line 28 to the secondary cyclone separator 26 in which further separation is accomplished. The'- catalyst separated in the secondary separator 2t passes to the catalyst hopper 32 through line 36.

Cracked products after being further purified of powdered material in the secondary cyclone separator 26 pass through line 2a to the tertiary iication and removal of powdered material therefrom. Powdered material recovered in the final separator 21 is transferred to the catalyst hopper t2 through line 35.

A line t6 is preferably provided connecting the top of the catalyst hopper 32 with the line 28 leading from the primary separator 25 to the secondaryseparator 26 so that gases collecting in the top of the catalyst hopper may be recombined with the cracked products. The cracked products from the 'nal separator 2li pass through line 31 to a fractionating tower @t wherein the products are fractionated to separately condense insuiiiciently cracked constituents. Condensate formed in the "ractionating tower 88 may be withdrawn from the bottom thereof through line 39V and returned to the cracng circuit for further cracking treatment or treated inany desired manner outside' of the purpose of the present invention.

Vapore remaining uncondensed in the fractionating tower 38 pass through line 4| to a condenser 42 wherein the desired motor fuel, distillate is condensed. Products from the condenser 82 pass through a receiver 43 wherein the desired distillate separates from uncondensed gases.L

i a screw conveyor Il.

The screw conveyor 48 may be of compression type capable of building up at least a portion of the pressure necessary to overcome the resistance of the system. In commercial size units of this type the pressure drop through the cracking and regenerating systems under normal operations may be of the order of from 10 to 30 pounds. The pressure on the catalyst necessary to overcome this resistance may be supplied by the screw conveyor Il or additional screw conveyors or other pressure providing means may be included in the circuit as later described. The catalyst passes from the screw conveyor Il into an'iniector chamber. wherein it is `picked up by a. stream of regenerating gas introduced through line 5l. The injector chamber may be of any desired construction which will permit intimate mixing of catalyst and regenerating gas. As illustrated, the chamber is 'provided with a conical disc having a central pipe through which the catalyst discharges into a mixing chamber located below the partition. The regenerating gas is preferably an oxidizing gas and may be air or air diluted with other' gases such as steam, spent combustion gases or the like.

The suspension of unregenerated catalyst and regenerating gas passes from the. injector 49 through line 5| to a regenerating chamber 52 maintained at thedesired temperature for burning thecarbonaceous deposits formed during the cracking operation from the catalyst. The temperature within the regenerating chamber shouldl perature within the regenerating chamber should preferably be maintained below 1100 F. This temperature can be controlled by regulating the `relative amounts of catalyst and oxidizing gas passing through the reaction chamber, by the provision of internal cooling elements within theregenerating chamber or in any other suitable manner.

The suspension of regenerating gas and. catalyst after passing through the regenerating chamber l2 passes through line 53 to a primary -'cy1one separator 5l in which the bulk of the regenerated catalyst is-separated from the regenerating gas. The catalyst so` separated is transferred through conduit 55 to a second catalyst hopper 58. Steam may be introduced into Aline 55 to strip regeneration gases from the powdered catalyst. l

` 'Ehe regenerating gas after having the .bulk of the catalytic material removed therefrom in the primary cyclone separator 54 passes through line 51 vto a secondary cyclone separator 58. wherein further separation is accomplished.Y Catalyst separated in the secondary separator $8 is trans- "ferred through line I! to the catalyst hopper 5I. Regenerating sa after being further purified in the secondary separator 58 is transferred through line il to a third cyclone separator 6l wherein separated in the final cyclone separator Gi is transferred through conduit 62 to the catalyst hopper It. The regenerating gas after having been substantially puried of regenerated catalyst in the final separator Il is rejected from the system through line il. This gas may be expanded through a turbine or it may be passed through suitable heat,l recovery system for removal of heat contained therein.

I'he regenerated catalyst collected in the catalyst hopper 56 is passed through line M having a suitable feeding mechanism such as a star feeder I5 `which feeds the material at the desired rate into a screw conveyor I6 which forces the material into the injector 2l from whence it is redispersed into the oil vapors to be cracked.

The screw conveyor Il may have a' compression screw for imposing a pressure necessary to overcome the pressure drop through the cracking system. In such case the screw conveyor Il may only supply suiiicient pressure to overcome the flow resistance through the regenerating section of the equipment. However. the amount of pressure necessary to overcome flow resistance 'may be provided by a single screw conveyor located either in the cracking or in the regenerating section of the equipment.

While screw conveyors have been described for supplying the required pressure for overcoming flow resistance, it will be understood that anyother equivalent devices may be employed. For example, the catalyst passing from the cracking to the regenerating sections of the equipment and vice versa maybe passed through double bell hoppers or other equivalent chambers in which the required pressure may be built up by means of a gas or steam.

The catalyst introduced into the oil stream may be at substantially the final regenerating temperature such as 1000. It is preferred to introduce the catalyst into the oil vapors at a temperature not materially below the temperature of the oil vapors and preferably somewhat'above so that a part of the heat necessary for crack ing may be supplied by the catalyst. Likewise, the catalyst introduced into the regenerating gas ing temperature which may be, for example, of

4 the order of 800-900" F.

final purification is accomplished. The catalyst In accordance with the present invention, the

pressuregdrop between the cracking and regenerating portions of the equipment is preferably maintained at the-minimum necessary to overcome the resistance through the equipment and should b e-less than one atmosphere. Furthermore, it is preferred to maintain both the cracking and regenerating portions of the equipment under a total pressure of the order of from 2 to 20 atmospheres gage while maintaining the partial pressure of the oil vapors leaving the cracking cracking operation. For example a portion of the gases separated in the receiver IlV may be recycledthrough line l1 and compressor Il and combined with the oil stream passing to the heating coil I! through line II or to the oil stream;

passing to the injector 2l through line 1l.

The invention thus makes possible the'cracking of oils in the presence of a powdered catalyst without the necessity oi! providing mechanism. between the cracking and regenerating circuits for building up a substantial differential pressure therebetween.

Having described the preferred embodiment of the invention it will be understood that it embraces such other variations and modifications as come within the spirit and scope thereof.

What is desired to be protected by Letters Patent is:

l. In the catalytic cracking of hydrocarbon oil wherein the catalyst is suspended in powdered form in a stream of oil vapors to be converted and the resulting stream passed through a cracking zone and wherein the catalyst after separation from the cracked products is passed through a regenerating` zone; the improvement which comprises maintaining both the cracking and the regenerating zones under a total pressure inexcess of two atmospheres and maintainl ing a partial pressure of oil vapors within the said cracking zone at not substantially exceeding one ucts and diluent gas, separating a' motor fuel fraction from the cracked products, passing the separated catalyst through a, regenerating zone wherein combustible deposits formed during the cracking operation are removed therefrom, maintaining the regenerating zone under a pressure substantially equal to total pressure maintained in said cracking zone and returning regenerated catalyst to said cracking zone.

3. A method of cracking hydrocarbon oil which comprises passing a mixture of hydrocarbon oil vapors boiling above the gasoline boiling range, diluentgas and iinely dividedcracking catalyst through a cracking zone maintained at cracking temperature, subjecting said mixture to a total pressure of atleast two atmospheres during passage through said cracking zone, regulating the molar concentration of the oil vapors and diluent gas to maintain the oil vapor pressure not substantially in excess of one atmosphere, maintaining said mixture within said cracking zone for a period sufiicient to obtain the desired cracking thereof into lower boiling hydrocarbons suitable for motor fuel, thereafter separating the catalyst from the cracked products and diluent gas, separating a motor fuel fraction from the cracked products, passing the separated catalyst through a regenerating zone wherein combustible deposits formed during the cracking operation are removed therefrom, maintaining the regenerating zone under a pressure substantially equal to the total pressure maintained in the cracking zone, and returning regenerated cat- A alyst to said cracking zone.

4. A method of cracking hydrocarbon oil which comprises passing a mixture of .hydrocarbon oil vapors boiling above the gasoline boiling range, diluent gas and finely divided cracking catalyst through a cracking zone maintained at cracking temperature, subjecting said mixture to a total pressure of at least two atmospheres during passage through the cracking zone, regulating the molar concentration of the oil vapors and dilul ent gas to maintain the oil v apor pressure not dit greater than about one atmosphere," maintaining said mixture'within said cracking zone for a period sucient to obtain the desired cracking thereof into motor fuel constituents, thereafter separating the catalyst from the cracked products and diluent gas, separating a motor fuel fraction from the cracked products, suspending the catalyst so separated in a regenerating gas,

passing the resulting suspension through 'a re- A generating zone wherein combustible deposits formed during the cracking operation. areremoved therefrom, maintaning the regenerating zone vunder a total pressure substantially equal to the pressure maintained in the cracking zone, separating regenerated catalyst from the regenerating gas, and returning the regenerated catalyst to the cracking zone.A

CHARLES W. TYsoN. CARL o. TONGBERG. 

